package calendartest

import (
	"strings"
	"testing"
	"time"

	calendar "amadan.net/oficina/calendar/internal/calendar"
)

// The sentence at the top of Today is the app's one opinion, so it gets
// a test rather than a hope. These assert the wording, because the
// wording IS the feature — a summary that says the right number in the
// wrong voice is a summary nobody reads twice.
func TestDaySummaryReadsLikeASentence(t *testing.T) {
	const tz = "UTC"
	day := time.Date(2026, 9, 2, 12, 0, 0, 0, time.UTC) // a Wednesday
	dayStart, dayEnd, err := calendar.DayBounds(day, tz)
	if err != nil {
		t.Fatalf("DayBounds: %v", err)
	}

	at := func(hh, mm int) int64 {
		return time.Date(2026, 9, 2, hh, mm, 0, 0, time.UTC).Unix()
	}
	ev := func(kind string, fromH, fromM, toH, toM int) calendar.EventView {
		return calendar.EventView{
			Event:       calendar.Event{Kind: kind},
			OccStartUTC: at(fromH, fromM),
			OccEndUTC:   at(toH, toM),
		}
	}

	t.Run("an empty day says so plainly", func(t *testing.T) {
		got := calendar.SummariseDay(day, nil, dayStart, dayEnd, tz).Sentence
		if got != "Wednesday. Nothing booked." {
			t.Errorf("sentence = %q", got)
		}
	})

	t.Run("one thing is not pluralised", func(t *testing.T) {
		got := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindMeeting, 9, 30, 10, 0),
		}, dayStart, dayEnd, tz).Sentence
		if !strings.HasPrefix(got, "Wednesday. One thing; the first at 09:30, the last ends at 10:00.") {
			t.Errorf("sentence = %q", got)
		}
	})

	t.Run("the gap is between the first and last, not the whole day", func(t *testing.T) {
		s := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindMeeting, 9, 30, 10, 0),
			ev(calendar.KindMeeting, 16, 0, 17, 0),
		}, dayStart, dayEnd, tz)
		// 09:30 to 17:00 is 7h30; 1h30 of it is booked; 6h free.
		if s.UnbookedMin != 360 {
			t.Errorf("UnbookedMin = %d, want 360", s.UnbookedMin)
		}
		if !strings.Contains(s.Sentence, "That leaves six hours unbooked between them.") {
			t.Errorf("sentence = %q", s.Sentence)
		}
	})

	t.Run("overlapping meetings do not consume the day twice", func(t *testing.T) {
		s := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindMeeting, 9, 0, 11, 0),
			ev(calendar.KindMeeting, 10, 0, 12, 0),
			ev(calendar.KindMeeting, 15, 0, 16, 0),
		}, dayStart, dayEnd, tz)
		// 09:00-12:00 merged is three hours, plus one at 15:00. The
		// span is 09:00-16:00, so three hours are free. Counting the
		// overlap twice would report four.
		if s.UnbookedMin != 180 {
			t.Errorf("UnbookedMin = %d, want 180 (the 10:00-11:00 overlap counted once)", s.UnbookedMin)
		}
	})

	t.Run("a full day says the alarming thing plainly", func(t *testing.T) {
		s := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindMeeting, 9, 0, 13, 0),
			ev(calendar.KindMeeting, 13, 0, 17, 0),
		}, dayStart, dayEnd, tz)
		if !strings.Contains(s.Sentence, "There is no unbooked hour between them.") {
			t.Errorf("sentence = %q", s.Sentence)
		}
	})

	// A birthday does not make a Tuesday fuller. Notes are excluded
	// from the arithmetic entirely.
	t.Run("notes do not occupy the day", func(t *testing.T) {
		s := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindNote, 9, 0, 10, 0),
		}, dayStart, dayEnd, tz)
		if s.Count != 0 {
			t.Errorf("Count = %d, want 0: a note is not a thing that occupies time", s.Count)
		}
		if s.Sentence != "Wednesday. Nothing booked." {
			t.Errorf("sentence = %q", s.Sentence)
		}
	})

	// The sentence must never contain a digit where a word was meant,
	// nor a stray fragment — the failure mode of assembling prose in
	// code is a sentence that is grammatical nonsense.
	t.Run("hours and minutes read as English", func(t *testing.T) {
		s := calendar.SummariseDay(day, []calendar.EventView{
			ev(calendar.KindMeeting, 9, 0, 9, 30),
			ev(calendar.KindMeeting, 11, 45, 12, 0),
		}, dayStart, dayEnd, tz)
		// 09:00-12:00 span, 45 minutes booked, so 2h15 free.
		if !strings.Contains(s.Sentence, "two hours and 15 minutes unbooked") {
			t.Errorf("sentence = %q", s.Sentence)
		}
	})
}